Not sure about this tie bar...Is it a natural stone or?

[macynmaddie]

Wondering if anyone can help me on this. What type of natural material does this consist of? Amber or ?
Thank you in advance for your time!

 

[stracci2000]

A handsome old necktie chain!
It is dendritic agate, a natural stone often used in vintage jewelry.
I have a small collection of this stone in assorted vintage pieces.

 

[Evgeniya]

it's definitely not amber